Finding an appropriate crystal for CY7C68013A (FX2LP)

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Anonymous
Not applicable

Hi,

   

 

   

I am using the CY7C68013A chip on our PCB, and was looking for an appropriate crystal to meet the required specifications as described in you application notes (point 4 on AN15456).

   

I am unable to find either crystal recommended in your app note or other crystals that meet the required specs of:

   

■ Parallel resonant
■ Fundamental mode
■ Frequency Stability: ±100 ppm
■ 500-uW drive level
■ 12pF (5% tolerance) load capacitors

   

 

   

Furthermore, the crystals used on the devboard CY3684 dev kit and the UPEK FISK USB reference design that incorporates the NX2LP chip (CY7C68033-56LFXC) do not meet the above specifications.

   

 

   

Could you please inform me whether it is necessary to use at least 500-uW drive level crystal, and whether I can use crystals with other load capacitances in my design.

   

 

   

Many Thanks,

   

Sach 

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1 Solution
Anonymous
Not applicable

Yes. It is recommended to use a crystal with that specifications.

   

The part that is there on the FX2LP DVK is: ECS-240-20-4. I think this part is available. Please check.

   

Regards,

   

sai krishna.

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9 Replies
Anonymous
Not applicable

Yes. It is recommended to use a crystal with that specifications.

   

The part that is there on the FX2LP DVK is: ECS-240-20-4. I think this part is available. Please check.

   

Regards,

   

sai krishna.

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Anonymous
Not applicable

 Can you please recommend a smaller package crystal that still meets the specs - the crystal you have sent me is very large!

   

 

   

Thanks

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Anonymous
Not applicable

 Hi,

   

 

   

Another thing : the part you have recommended (as used on the dev board) has a 20pF load capacitance (where 12pF is recommended in the applciation note) - so am I right in thinking it doesn't matter what load capacitance crystal we use with the chip?

   

 

   

Thanks 

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Anonymous
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It has to do with the crystal startup. FX2LP has been extensively tested with 12pF load. So please use a 12 pF load.

   

Regards,

   

Anand

Anonymous
Not applicable

Hi Anand,

   

 I really don't get it though, why have you used a 20pF crystal on the dev board for FX2LP?    I would really appreciate it if you could even give me an example of a (small) part that has a load capacitance of 12pF and drive level of 500uW as none of our suppliers (RS components, digikey, farnell, mouser) seem to have such a product (in mass supply greater than quantities of 250) on a glance through their product catalogs.

   

 

   

The following crystals appear to meet the specs, but they may be close to end of line as their stocks are low...

   

http://uk.farnell.com/aker/c7s-24-000-12-3030-x/crystal-smd-ceramic-24-000mhz/dp/1538819

   

http://uk.farnell.com/aker/c6s-24-000-12-3030-x/crystal-smd-cer-24-000mhz/dp/1538833

   

Many Thanks 

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Bob_Marlowe
Level 10
Level 10
First like given 50 questions asked 10 questions asked

Isn't there a capacitance of ~7pF at the Pin itself which gives about 20pF together with the 12pF capacitor? As such, you'll need a 20pF x-tal.

   

 

   

Bob

Anonymous
Not applicable

Oh of course!!!!!! Excuse my ignorance.  Many thanks for the clarification

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Bob_Marlowe
Level 10
Level 10
First like given 50 questions asked 10 questions asked

Glad to have helped you!

   

Bob

Anonymous
Not applicable

Hi,

   

we have a similarly problem. We implemented a CY7C68013A-56 in our design and now we are looking for a crystal in 3.2x2.5 case.

   


I'm a bit confused because the FX2LP DMB-T/H TV Dongle Reference Design also use a 3.2x2.5 crystal (Hosonic E3SB 24.000 18pF) that is able to handle 100uW(200uW max) without any damping resistor in the circuit. What is the "normal" drive level of FX2LP?

   

Is this a proper solution? I think the Hosonic crystal will be very similarly to ABM8, which is a good available part, just the shunt capacitance deviates.

   

 

   

Best regards

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